Showing papers on "Network topology published in 1981"
TL;DR: Various network topologies and switching strategies are covered here, including interconnection networks for communication among processors and memory modules.
Abstract: Concurrent processing depends on interconnection networks for communication among processors and memory modules. Various network topologies and switching strategies are covered here.
859 citations
TL;DR: In this article, a new model for the study of power system stability via Lyapunov functions is proposed, which is an assumption of frequency-dependent load power, rather than the usual impedance loads which are subsequently absorbed into a reduced network.
Abstract: A new model for the study of power system stability via Lyapunov functions is proposed. The key feature of the model is an assumption of frequency-dependent load power, rather than the usual impedance loads which are subsequently absorbed into a reduced network. The original network topology is explicitly represented. This approach has the important advantage of rigorously accounting for real power loads in the Lyapunov functions. This compares favorably with existing methods involving approximations to allow for the significant transfer conductances in reduced network models. The preservation of network topology can be exploited in stability analysis, with the concepts of critical and vulnerable cutsets playing central roles in dynamic and transient stability evaluation respectively. Of fundamental importance is the feature that the Lyapunov functions give a true representation of the spatial distribution of stored energy in the system
641 citations
IBM1
TL;DR: A comparative evaluation of the performance of ring and bus systems constituting subnetworks of local-area networks, based on analytic models which describe the various topologies and access mechanisms to a sufficient level of detail.
Abstract: This paper provides a comparative evaluation of the performance of ring and bus systems constituting subnetworks of local-area networks. Performance is measured in terms of the delaythroughput characteristics. Systems investigated include token-controlled and slotted rings as well as random-access buses (CSMA with collision detection) and ordered-access buses. The investigation is based on analytic models which describe the various topologies and access mechanisms to a sufficient level of detail. The paper includes a comprehensive discussion of how the performance of the different networks is affected by system parameters like transmission rate, cable length, packet lengths, and control overhead.
412 citations
TL;DR: It is argued that flooding schemes have significant drawbacks for such networks, and a general class of distributed algorithms for establishing new loop-free routes to the station for any node left without a route due to changes in the network topology is proposed.
Abstract: We consider the problem of maintaining communication between the nodes of a data network and a central station in the presence of frequent topological changes as, for example, in mobile packet radio networks. We argue that flooding schemes have significant drawbacks for such networks, and propose a general class of distributed algorithms for establishing new loop-free routes to the station for any node left without a route due to changes in the network topology. By virtue of built-in redundancy, the algorithms are typically activated very infrequently and, even when they are, they do not involve any communication within the portion of the network that has not been materially affected by a topological change.
386 citations
TL;DR: This paper compares nine network interconnection schemes and introduces "dual-bus hypercubes," a cost-effective method of connecting thousands of dual-port single-chip microcomputers into a room-sized information processing system, a "network computer."
Abstract: This paper compares nine network interconnection schemes and introduces "dual-bus hypercubes," a cost-effective method of connecting thousands of dual-port single-chip microcomputers into a room-sized information processing system, a "network computer." Each network node is a chip containing memory and a pair of processors for tasks and input/output. Nodes are linked by shared communication buses, each conceptually spanning a D-dimensional, W-wide hypercube of N = WD nodes. Each node shares two buses. Each bus is shared by up to W nodes. The number of bus connections per node is fixed to satisfy chip pin limitations.
288 citations
01 Dec 1981
TL;DR: LOCUS is a distributed operating system that provides a very high degree of network transparency while at the same time supporting high performance and automatic replication of storage and Atomic file operations and extensive synchronization are supported.
Abstract: LOCUS is a distributed operating system that provides a very high degree of network transparency while at the same time supporting high performance and automatic replication of storage. By network transparency we mean that at the system call interface there is no need to mention anything network related. Knowledge of the network and code to interact with foreign sites is below this interface and is thus hidden from both users and programs under normal conditions. LOCUS is application code compatible with Unix2, and performance compares favorably with standard, single system Unix. LOCUS runs on a high bandwidth, low delay local network. It is designed to permit both a significant degree of local autonomy for each site in the network while still providing a network-wide, location independent name structure. Atomic file operations and extensive synchronization are supported.Small, slow sites without local mass store can coexist in the same network with much larger and more powerful machines without larger machines being slowed down through forced interaction with slower ones. Graceful operation during network topology changes is supported.
269 citations
01 Jan 1981
TL;DR: The theoretical basis for determining the bad measurement detectability properties of the state estimator from the topology of the 1-line diagram and the locations of the measurements is developed.
Abstract: A power system static-state estimator has the ability to detect and purge some measurement errors. This paper develops the theoretical basis for determining the bad measurement detectability properties of the state estimator from the topology of the 1-line diagram and the locations of the measurements. Based on this theory, an algorithm is described that: 1) identifies those measurements that have detectable error residuals; and 2) determines the regions of measurement error residual spread.
157 citations
TL;DR: The cube network can support both MIMD and SIMD processing in distributed systems and allows flexible communications in systems like PASM, PUMPS, and the BMD test bed.
Abstract: The cube network can support both MIMD and SIMD processing in distributed systems. It allows flexible communications in systems like PASM, PUMPS, and the BMD test bed.
134 citations
TL;DR: The results indicate that a desirable length of talkspurt "hangover" of about 200 ms will accomplish this without unduly affecting speech activity, and that, under these circumstances, the perceptable threshold of variable talkpurt delay can be as high as about 200ms average.
Abstract: This paper focuses on network delays as they apply to voice traffic. First the nature of the delay problem is discussed and this is followed by a review of enhanced circuit, packet, and hybrid switching techniques: these include fast circuit switching (FCS), virtual circuit switching (VCS), buffered speech interpolation (SI), packetized virtual circuit (PVC), cut-through switching (CTS), composite packets, and various frame management strategies for hybrid switching. In particular, the concept of introducing delay to resolve contention in SI is emphasized, and when applied to both voice talkspurts and data messages, forms a basis for a relatively new approach to network design called transparent message switching (TMS). This approach and its potential performance advantages are reviewed in terms of packet structure, multiplexing scheme, network topology, and network protocols. The paper then deals more specifically with the impact of variable delays on voice traffic. In this regard the importance of generating and preserving appropriate length speech talkspurts in order to mitigate the effects of variable network delay is emphasized. The results indicate that a desirable length of talkspurt "hangover" of about 200 ms will accomplish this without unduly affecting speech activity, and that, under these circumstances, the perceptable threshold of variable talkspurt delay can be as high as about 200 ms average. As such, the results provide a useful guideline for integrated services system designers. Finally, suggestions are made for further studies on performance analysis and subjective evaluation of advanced integrated services systems.
94 citations
TL;DR: Two heuristic reliability indices are presented which give a fair indication of overall reliability and a design procedure for reliable computer communication network based on local search technique incorporating these reliability indices is suggested.
Abstract: Incorporating network reliability parameter in the design of reliable computer communication networks makes the computations prohibitive. Interdependence among network topological parameters does not permit the design of a maximally reliable network using any one of the parameters and thus, there arises a real need for a composite reliability index which gives a more realistic assessment of network reliability. After discussing experimental results regarding the effects of various topological parameters on network reliability, we present two heuristic reliability indices which give a fair indication of overall reliability. A design procedure for reliable computer communication network based on local search technique incorporating these reliability indices is suggested. Having only one composite reliability index which is very simple to evaluate saves computation while designing maximally reliable computer networks as compared to the existing techniques based on several reliability measures.
39 citations
01 Oct 1981
TL;DR: This paper includes derivation of closed form expressions for the maximum and average hop distance between nodes, number of distinct routes between two farthest nodes, and throughput.
Abstract: @, where N is the number of nodes in the network. We show that this network is optimal in terms of hop distance between nodes, delay, throughput, and terminal reliability. The paper includes derivation of closed form expressions for the maximum and average hop distance between nodes, number of distinct routes between two farthest nodes, and throughput. The effect of node and link failures on network performance is also considered.
TL;DR: Performance considerations, particularly network delays, for integrated voice and data networks are reviewed and the concept of introducing delay to resolve contention in SI is emphasized and forms a basis for a relatively new approach to network design called transparent message switching (TMS).
01 Dec 1981
TL;DR: In these notes, some aspects of routing and flow control for long-haul wire data networks in which the communication resource is scarce, and where there are no issues of contention resolution due to random access of a broadcast medium are considered.
Abstract: : The main purpose of routing and flow control in a communication network is, roughly speaking, to keep delay per message within an acceptable level while minimizing the amount of offered traffic that is rejected by the network due to its inability to handle it. These two objectives are clearly contradictory so a good routing and flow control scheme must strike a balance between the two. It should also take into account a number of other issues such as fairness for all users, the possibility that the network topology can be altered due to unexpected link or node failures, and the fact that the statistics of offered traffic change with time. In these notes we consider some aspects of routing and flow control for long-haul wire data networks in which the communication resource is scarce (as opposed to local networks such as Ethernet where it is not), and where there are no issues of contention resolution due to random access of a broadcast medium (as in some satellite, local, and packet radio networks). We place primary emphasis on optimal procedures since these offer a more sound philosophical basis than heuristic schemes and also provide a yardstick for measuring the effectiveness of other methods.
TL;DR: It is concluded that in the near future there are valid technical and non-technical reasons for adding data traffic to the office voice networks, and that the combined network should be based on a star topology.
01 Dec 1981
TL;DR: Lumped/distributed networks are analysed using state-space techniques and the time response, for any set of inputs, is obtained without the need of either the explicit form of the transfer function or the use of convolution.
Abstract: Lumped/distributed networks are analysed using state-space techniques. The state and output equations are derived using topological methods with no restrictions on the topology. The method is applied to noncommensurate circuits and to coupled transmission-line circuits in inhomogeneous media. Computer programs have been developed for the analysis of these circuits in both the frequency and time domains. The time response, for any set of inputs, is obtained without the need of either the explicit form of the transfer function or the use of convolution.
12 May 1981
TL;DR: The mechanism presented is shown to reduce significantly the amount of computational work required in software allocation of resources and supports differing network topologies and decentralized scheduling.
Abstract: The allocation of resources in an array computer using either an SW-banyan or a tree interconnection network is implemented in hardware. A generalized solution for the resource allocation problem in such machines is presented. The solution reduces network node blockage and node distances and supports differing network topologies and decentralized scheduling. The mechanism presented is shown to reduce significantly the amount of computational work required in software allocation of resources.
TL;DR: Networks using Intel's Local Network Architecture promise significant benefits in resource sharing, communications multiplexing, and distributed computing.
Abstract: Networks using Intel's Local Network Architecture promise significant benefits in resource sharing, communications multiplexing, and distributed computing.
TL;DR: The numbers of mutations along the single branches of the network may not uniquely be determined by sequence data and network topology, however, their sum is unique and is a measure for the probability to describe evolution properly, assigned to this network by the maximum parsimony hypothesis.
01 Jun 1981
TL;DR: The application of communication structures to advanced transport aircraft are addressed and multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems.
Abstract: Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems.
01 Jan 1981
TL;DR: A new mechanism for a distributed database management system that allows nonstop operation under a network partition and considers external actions that may be performed in response to transactions on the database system and restricts them in a way that prevents inconsistencies at partition merge.
Abstract: This dissertation proposes a new mechanism for a distributed database management system that allows nonstop operation under a network partition
It the network that supports a distributed database with redundant data becomes partitioned, independent updates may cause inconsistencies to arise Existing solutions to this problem totally block updates in all but one partition, in which case mutual consistency can be easily obtained upon partition merge by propagating the updates In systems for which updates are essential, these solutions are often unacceptable because system availability is reduced
The approach proposed allows mutual consistency to be violated in a controlled way such that database reconciliation can be made automatically by the DBMS In addition to obtaining mutual consistency after partition merge, this approach also considers external actions that may be performed in response to transactions on the database system and restricts them in a way that prevents inconsistencies at partition merge
The method is based on the division of database operations into classes of semantics Five classes are defined, and a merge algorithm is provided for each class Strong data types and integrity assertions are used to enforce semantic integrity The assertions to be enforced may vary dynamically according to the network topology As the semantic freedom of the operations increases, so does the complexity of the merge algorithms
To demonstrate the feasibility of this approach we present a case study involving an electronic funds transfer system For this system, only the two simplest classes of semantics, which involve very little overhead, were necessary to support all the required operations
The mechanism proposed allows normal operation to proceed while the database reconciliation algorithms are executing and partial partition merges
12 May 1981
TL;DR: This paper proposes the optimal processor interconnection topologies for parallel processing that are optimal with respect to the performance/cost ratio under the controlled message transfer delay and can be systematically constructed for an arbitrary number of processors.
Abstract: This paper proposes the optimal processor interconnection topologies for parallel processing. The topologies are optimal with respect to the performance/cost ratio under the controlled message transfer delay and can be systematically constructed for an arbitrary number of processors. The addition and the deletion of processors are simple and done with the minimum number of bus reconnections. The message transfer delay, as well as the reliability, can be controlled by changing the degree of the topology. Owing to these properties, the optimal interconnection topologies are suitable for many kinds of parallel processing systems and algorithms.
TL;DR: The main result indicates that permuting, coupling, and partitioning capabilities can be obtained by using 2, 3, and 4-state cells, respectively, in a large class of network topologies.
Abstract: Investigates generalizations of triangular permuting networks in two directions: the connecting power of cells and the network topology. The main result indicates that permuting, coupling, and partitioning capabilities can be obtained by using 2-, 3-, and 4-state cells, respectively, in a large class of network topologies.
01 Jan 1981
TL;DR: To define regions in digital image the authors use topological notion of connectivity, which refers to the existence and the description of a topology.
Abstract: To define regions in digital image we use topological notion of connectivity. This notion refers to the existence and the description of a topology.
TL;DR: The definitions and properties of well-known network topology for the three-dimensional case are extended and its network dual and retrieval dual, as defined later, are interesting and useful.
TL;DR: Some promising techniques for the future of security functions in power system control centres are presented, such as the implementation of on-line “compact” optimal power flows and the inclusion of transient stability constraints into on- line optimalPower flows.
15 Jun 1981
TL;DR: In this paper, the authors propose a state-space technique for constructing microwave networks in the time domain using state space techniques with no restrictions on the network topology. Computer-aided procedures are used to optimise the time-domain responses.
Abstract: Commensurate transmission-line networks are designed in the time domain using state-space techniques with no restrictions on the network topology. Computer-aided procedures are used to optimise the time domain responses. Several examples are given of microwave networks designed using this technique.
TL;DR: A dynamic programming algorithm for minimum hop flow assignment in message-switched telecommunication networks is developed and is a significant improvement over previous ones since it is applicable to any network topology, to anySet of link capacities, and to any set of traffic requirements.
TL;DR: In this article, it was shown that 2 2 c non-isomorphic group topologies on the real line are non-locally compact, connected, locally compact and compactly generated.
TL;DR: This paper presents a comprehensive discussion of issues involved and trends prevailing in producing reliable hardware; reliable software; and reliable computer communication network while reviewing techniques available for preventing, detecting, diagnosing, correcting and recovering from malfunctions.
01 Jan 1981
TL;DR: This dissertation considers the development of a generalized model of the network design process that proposes that the physical and logical network components can be described using a set of objects, properties and relationships.
Abstract: The increase in the interconnection of computers has led to a corresponding increase in the complexity of effective network design. This increase is partly to the size and diversity of computer networks, but also is due to the proliferation of available network hardware and software.
As with any system, computer networks are made up of various interrelated components, all of which are essential to the network design process. Some of these components are physical in nature, that is, they specify a piece of hardware or software with certain perfomance properties. Other components are considered to be logical elements of network design.
The problem of designing, implementing and controlling present and planned data communication networks is rapidly exceeding manual planning and design capabilities. Network managers and designers are looking more and more to computer resources to manage the volume of traffic information, to develop and evaluate network configurations, and to assist in allocating and placing control functions among network processors.
The number of network alternatives is increasing so fast that the demand for network optimization--both in private network design and in the interface to, and use of, public network facilities--can be satisfied only through computer aids. These aids range from simple scratch-pad systems that store and compile network statistics to complete traffic emulators, design configurators, and software for data-distribution modelling.
Network design generates a set of performance/cost tradeoffs for an existing or proposed network. The network design process generates and regenerates these performance curves in response to changes in critical design parameter such as protocols, line capacity, concentration points, host processor capability and message routing techniques.
This dissertation considers the development of a generalized model of the network design process. This model proposes that the physical and logical network components can be described using a set of objects, properties and relationships. Objects are used to describe network physical and logical components. These components are given properties, thus associating with each object a set of network descriptions. Linkages between objects or classes of objects are provided by object-object relationships. The prototype system provides a generalized network design tool which allows a concise and explicit statement of network requirements providing a network planning and design model which is independent of any particular network or application.